Brain structure + linked to aggression Flashcards
lateralisation
- brain is in 2 halves (hemispheres)
how are the 2 hemispheres of the brain joined together
corpus callosum
Corpus callosum
- part of the brain that passes messages between the 2 hemispheres
- acts as a communication system
what would happen if the corpus callosum got damaged
there would be no way of the 2 hemispheres of the brain from working together
Corpus Callosum composition
- white matter = myelinated nerve cells /axons,
- whose function is to connect grey areas together with neural impulses
Lobes of the brain, in order - start with frontal
- frontal lobe
- parietal lobe
- occipital lobe
- cerebellum
- brain stem
- temporal lobe
Frontal lobe
- thinking
- planning
- problem solving
- emotions
- behavioural control
- decision making
Parietal lobe
- Perception
- object classification
- spelling
- knowledge of numbers
Occipital lobe
- visual processing
- vision
- colour identification
Cerebellum
- gross and fine movements
- hand eye coordination
- balance
brain stem
- regulates body temperature
- heart rate
- swallowing
- breathing
Temporal lobe
- memory
- understanding
- language
- hearing
Phineas Gage
- pre frontal lobe damaged with a rod
- changed his personality
- making him more aggressive
Limbic system
- a complex set of structures of the brain that lie on either side of the thalamus
- associated with emotional processing and behaviour
- satisfies motivational and emotional urges
Main structures of limbic system
- hypothalamus
- hippocampus
- amygdala
- cingulate cortex.
where is the prefrontal cortex located
frontal lobe
Pre frontal cortex
- attention and focus
- personality expression
- planning of complex cognitive behaviours
- has an input to our emotional responses
- controls our social inhibitions
- acts as a voice of reason
- involved in making rational decisions over impulsive ones
when is the pre frontal cortex finally developed
mid 20s
what part of the brain does aggression appeared to be associated with
limbic system
Amygdala
- responsible for quickly evaluating the emotional importance of sensory information and prompting an appropriate response
- plays a central role in how an organism asses and responds to environmental threats and challenges
- it is an important predictor of aggressive behavior
what happens if certain areas of the amygdala are stimulated electrically
an animal responds aggressively
Hippocampus
- involved in the formation of long-term memories
- allows animals to compare the conditions of a current threat with similar past experiences`
Brain dysfunction - what would damage to the pre frontal cortex result in
- impulsivity
- immaturity
- altered emotions
- loss of self control
- inability to modify behaviour
- increasing aggression
how is the amygdala associated with aggression
- as it is used to recognise emotional stimuli
- could lead to fearlessness
- may lead to inability to form conditioned emotional responses and failure to learn from experiences
what did Raine find in terms of the amygdala
- There is an interaction between the prefrontal cortex and the amygdala as the PFC acts on the amygdala to suppress fear.
Bear - Amygdala
Bear (1991): If destroyed in animals they lack fear. If destroyed in humans it reduces the autonomic arousal leading to fearlessness
Kluver and Bucy - amygdala
Kluver & Bucy: lesions in the medial temporal lobe in monkeys abolished their aggressive behaviour
Hypothalamus - Alpers; affect on humans
- Studied a liked, well mannered middle aged lawyer
- He has a temporal medial hypothalamus
- Resulted in aggressive outbursts
Hypothalamus - Hess ; effect on animals
Induced aggressive behaviour (biting attacks) in cats and rats by electrical stimulation of the hypothalamu, specifically the hypothalamic attack area.
aggression
any action that is aimed at causing either physical and or psychological pain to oneself or others or objects in the environment
Purposes of aggression
- express hostility
- Assert dominance
- Intimidate
- Response to fear
- Competition
- Reaction to pain
Raine et al aim
To investigate whether brain dysfunction predisposed people to violent behaviour
Raine et al sample
- Two groups of ppts: Group 1 41 murderers pleading not guilty by reason of insanity (39 men and 2 women) either charged with murder or manslaughter.
- Group 2 (control) 41 ppts matched sex, age and other similarities.
- None were on medication, including control group.
- Matched pairs design used
Raine et al - IV
whether participant was a murderer or not
Raine et al - DV
measure of brain activity using a PET scan
Raine et al - Findings
- NGRIs showed less activity in the frontal lobe especially the prefrontal cortex
- less activity in the parietal lobe
- NGRIs had less activity in the corpus callosum
- an imbalance of activity between the left and right hemispheres in the limbic system
- less activity on the left and more on the right in the amygdala and hippocampus; more activity on the right side of the thalamus
- These are areas of the brain associated with aggression in animals
Raine et al - conclusions
- Raine suggests how the brain abnormalities in the murderers might translate into violence or anti-social behaviour
- Prefrontal deficits (deficits are lack of activity) might make someone more impulsive and emotional
- Deficits in the limbic system might make someone aggressive
- Deficits might make it hard for someone to learn from mistakes or understand their emotions.
- Deficits in the corpus callosum make it harder for the brain’s hemispheres to communicate, making it difficult to think through long term consequences and make decisions - Areas like the parietal lobe, amygdala and hippocampus have a part to play in recognition; deficits here might make it harder for someone to judge social situations, leading them to overreact.
Strengths - Brain scan research
- Animals limbic systems function similarly to humans as the limbic system in humans is seen as the old part of the brain
- Credibility due to high reliability of research
Weaknesses - brain scanning research
- generalisability issues
- ethical and practical issues
- case studies
Applications
- gives us a better understanding of neural influences on aggression
- serenics is a drug that has been developed to affect the brains serotonin system and decrease aggression with minimal side effects
- useful as human aggression is the root of many personal,
social and economic costs
Reductionist
- narrow focus on biological factors is reductionist
- amygdala is not an inevitable cause of aggression it also depends on social, psychological and environmental factors
- biological factors isn’t enough to trigger aggression
- reductionist explanation doesn’t reflect the complexity of the causes of aggression
